Ezreal reduces only optional additional costs you choose to pay. These costs use both the word "may" and the exact phrase "as an additional cost."^356.2.b.1 [Accelerate] and [Repeat] are optional additional cost keywords, so Ezreal reduces them too.^805.1^820.1

Ezreal's discount applies to the optional additional cost itself as soon as that cost is added, and only to the chosen component, before discounts that apply to the card's total cost.^356.4.c^356.4.c.1^356.4.d

Mandatory additional costs are not optional because they omit "may," so Ezreal does not reduce them.^356.2.a.1 Hard Bargain's resource payment happens while carrying out its effect as the spell resolves.^158.1 It is not an additional cost to play Hard Bargain, so Ezreal does not reduce it.^204.2²⁰⁵

Example

Blast Corps Cadet says "You may pay 1 as an additional cost to play me." Ezreal can reduce that optional additional cost to either 1 or . By contrast, Ezreal does not reduce Cruel Patron's mandatory cost to kill a friendly unit or the 2 an opponent may pay during Hard Bargain's effect. Ezreal does reduce Hard Bargain's separate [Repeat] cost.

From Riftbound FAQ by Christian “Near” Ivicevic, licensed CC BY-SA 4.0. Reviewed against Core Rules 1.5. Unofficial; not from Riot Games.